我有一个缓冲区,其中包含YV12格式的图像。现在我要将此缓冲区转换为RGB格式或直接从中创建Mat对象!有人能帮我吗?我试过这段代码:
cv::Mat input(widthOfImg, heightOfImg, CV_8UC1, vy12Buffer);
cv::Mat converted;
cv::cvtColor(input, converted, CV_YUV2RGB_YV12);
这不可能。
Y'UV420p是平面格式,意味着Y',U和V值被组合在一起而不是散布。这样做的原因是通过将U和V值分组在一起,图像变得更加可压缩。当给出Y'UV420p格式的图像阵列时,所有Y'值首先出现,然后是所有U值,最后是所有V值。
但是cv::Mat
是一个RGB颜色模型,并且像B0 G0 R0 B1 G1 R1那样排列......所以,我们不能直接从YV12缓冲区创建一个Mat对象。
这是一个例子:
cv::Mat Yv12ToRgb( uchar *pBuffer,long bufferSize, int width,int height )
{
cv::Mat result(height,width,CV_8UC3);
uchar y,cb,cr;
long ySize=width*height;
long uSize;
uSize=ySize>>2;
assert(bufferSize==ySize+uSize*2);
uchar *output=result.data;
uchar *pY=pBuffer;
uchar *pU=pY+ySize;
uchar *pV=pU+uSize;
uchar r,g,b;
for (int i=0;i<uSize;++i)
{
for(int j=0;j<4;++j)
{
y=pY[i*4+j];
cb=ucharpU[i];
cr=ucharpV[i];
//ITU-R standard
b=saturate_cast<uchar>(y+1.772*(cb-128));
g=saturate_cast<uchar>(y-0.344*(cb-128)-0.714*(cr-128));
r=saturate_cast<uchar>(y+1.402*(cr-128));
*output++=b;
*output++=g;
*output++=r;
}
}
return result;
}
那是可能的。
cv::Mat picYV12 = cv::Mat(nHeight * 3/2, nWidth, CV_8UC1, yv12DataBuffer);
cv::Mat picBGR;
cv::cvtColor(picYV12, picBGR, CV_YUV2BGR_YV12);
cv::imwrite("test.bmp", picBGR); //only for test
高度乘以3/2,因为有4个Y样本,每2x2平方像素存储1 U和1 V样本。这导致字节样本与像素的比率为3/2
4*1+1+1 samples per 2*2 pixels = 6/4 = 3/2
更正:在最新版本的OpenCV(我使用最旧的2.4.13版本)中,颜色转换代码更改为COLOR_YUV2BGR_YV12
cv::cvtColor(picYV12, picBGR, COLOR_YUV2BGR_YV12);
这是java(Android)中的相应版本...
此方法比其他技术(如renderscript或opengl(glReadPixels))更快,可以从yuv12 / i420数据流中获取位图(使用webrtc i420测试)。
long startTimei = SystemClock.uptimeMillis();
Mat picyv12 = new Mat(768,512,CV_8UC1); //(im_height*3/2,im_width), should be even no...
picyv12.put(0,0,return_buff); // buffer - byte array with i420 data
Imgproc.cvtColor(picyv12,picyv12,COLOR_YUV2RGB_YV12);// or use COLOR_YUV2BGR_YV12 depending on output result
long endTimei = SystemClock.uptimeMillis();
Log.d("i420_time", Long.toString(endTimei - startTimei));
Log.d("picyv12_size", picyv12.size().toString()); // Check size
Log.d("picyv12_type", String.valueOf(picyv12.type())); // Check type
Utils.matToBitmap(picyv12,tbmp2); // Convert mat to bitmap (height, width) i.e (512,512) - ARGB_888
save(tbmp2,"itest"); // Save bitmap
您可以尝试YUV_I420阵列
char filePath[3000];
int width, height;
cout << "file path = ";
cin >> filePath;
cout << "width = ";
cin >> width;
cout << "height = ";
cin >> height;
FILE *pFile = fopen(filePath, "rb");
unsigned char* buff = new unsigned char[width * height *3 / 2];
fread(buff, 1, width * height* 3 / 2, pFile);
fclose(pFile);
cv::Mat imageRGB;
cv::Mat picI420 = cv::Mat(height * 3 / 2, width, CV_8UC1, buff);
cv::cvtColor(picI420, imageRGB, CV_YUV2BGRA_I420);
imshow("imageRGB", imageRGB);
waitKey(0);